EDM or electrical discharge machining, is a type of machining method that is often used when working with hard metals or those that will be extremely hard to machine with normal techniques. A big limitation of EDM though is that it can only be used with materials that can conduct electricity. EDM is a great machining method to use when cutting complex contours or delicate cavities that can be hard to make using a grinder, an end mill or other cutting implements. Some of the metals that can be machined using the EDM method include hardened tool-steel, titanium, hastalloy, carbide, inconel and kovar.
EDM is also known as spark machining because the method removes metal by producing a fast and repetitive series of electrical discharge. The electrical discharge is transmitted between the electrode and the metal being worked on. The small pieces of metal that are removed from the material that is worked on is also flushed with fluid that continuously flows through are being worked on. The repeated discharges makes a set of craters that get successively deeper until the final shape is produced on the metal piece.
EDM can be divided into two main methods – ram EDM and wire EDM. The main difference between these two methods largely involves the electrode employed when machining the metals. In a ram EDM method, the graphite electrode is machined using traditional machining tools. The electrode, which has now been shaped according to the specific need, is connected to the power source and then attached to a ram. This is then fed slowly to the metal being worked on. The whole machining operation is usually done while the whole thing is submerged in a fluid bath.